Drainage devices may be implanted to treat various conditions. For example, drainage stents configured as biliary stents may be implanted in the biliary tract to treat obstructive jaundice. FIG. 1 is illustrative of a typical biliary system showing: a right hepatic duct 1a joining with the left hepatic duct 1b to form a common hepatic duct 6; a gall bladder 5 and a cystic duct 3; a pancreas 7 and a pancreatic duct 9; and all aforementioned ducts connecting to form a common bile duct 2 leading to a duodenum 4 through the Papilla of Vater 8 and Sphincter of Oddi. Biliary stenting treatment approaches can be used to provide short-term treatment of conditions such as biliary fistulae or giant common duct stones. Biliary stents may be implanted to treat chronic conditions such as postoperative biliary stricture, primary sclerosing cholangitis and chronic pancreatitis. An implanted biliary stent may permit digestive liquids to flow through the biliary stent lumen into the duodenum and the digestive tract.
A drainage device, such as a drainage stent or catheter, can be configured as a tubular member defining a drainage lumen that can be advanced on a delivery system into a body vessel, such as the bile duct, where the drainage device is deployed. Typically, the tubular member includes one or more perforations communicating between an exterior surface of the tubular member and the drainage lumen. The tubular member preferably has sufficient radial strength to resist collapse and to maintain an open body vessel lumen upon implantation. The tubular member is preferably longitudinally flexible enough to be advanced during delivery along a guidewire through a path that may include sharp bends.
To secure the drainage stent at a site of implantation within the body vessel, the tubular member may include a means for retaining the drainage stent within a body vessel, such as retention flaps radially projecting from the tubular body. Retention flaps may be formed by making an oblique slit along the length of the tubular member. Each slit defines a tab and enables the tab to project slightly radially outwardly of the outer surface of the tube to engage the luminal surface of the biliary duct to prevent migration. The tabs at the opposite ends of the drainage stent typically extend toward the middle of the stent as well as radially outward. The openings defined by the tab-forming skives may provide access to the interior of the stent of cellular or other material that may tend to develop into an obstruction tending to restrict flow through the stent. Alternatively, drainage stents may include one or more curled or coiled end portions. For example, the distal and/or proximal ends of a drainage stent may have a curled configuration, often referred to as a “pigtail” configuration. One such example is shown by U.S. Pat. No. 5,052,998 to Zimmon which discloses an indwelling drainage stent having flaps at one end, a series of drainage perforations along the length of the drainage stent and a pigtail configuration at the opposite end. Other stents include anchoring flaps or pigtail loops at both ends of the stent. Prior art stents have been provided both with and without the drainage perforations as shown in the Zimmon patent. Other structures, such as helical tubular drainage stents having an inflatable portion, are disclosed by Rucker in US 2006/0167538A1, filed Dec. 21, 2005. Kolb describes drainage stents having one or more curled portions and a drainage channel having a laterally open portion in US 2006/0052879 A1, filed Aug. 16, 2005.
Tubular biliary stents are typically implanted with a delivery system having the stent mounted on the distal end of a guidewire. After the stent has been advanced along a guidewire and manipulated into the intended deployment site in the biliary duct, the stent is released and the delivery device is retracted, thereby leaving the stent within the biliary tract. For example, biliary drainage stents are typically advanced on a delivery catheter through an endoscope and deployed in a bile duct. Biliary and pancreatic stents are typically pushed into place by a “pusher” catheter which is advanced from behind the stent and pushes against the proximal end of the stent until the stent has reached its desired location. The distal end of the delivery catheter generally must pass through the Papilla of Vater, for example by passing a drainage stent through the Sphincter of Oddi. An uncompromised Sphincter of Oddi acts a one-valve letting biliary drainage to flow only toward the duodenum.
However, during the placement procedure, conventional structures for retaining the drainage stent within the body passage, such as flaps or curled ends, may irritate ductal tissue as they pass through the duct, which may lead to inflammation of the duct. Conventional drainage stent structures for retaining the drainage stent in position after implantation may also cause aggravation to the ductal tissue while the stent is left in place, or when the drainage stent is removed. Furthermore, insertion of a drainage stent placed by endoscopic sphincterotomy may require stretching and cutting of the Sphincter of Oddi and surrounding areas, which may compromise the function of the Sphincter of Oddi after insertion of the drainage stent. In addition to the sphincterotomy procedure for inserting a drainage stent, placement of the position of the biliary stent at the Papilla of Vater (e.g., across the Sphincter of Oddi) may also lead to duodenobiliary reflux. A compromised Sphincter of Oddi may allow fluid flow in the reverse direction from the duodenum, or duodenobiliary reflux, causing bacteria and biofilm deposition, and possibly occluding the biliary duct or the drainage stent.
Therefore, there exists a need for an improved drainage device which can be retained within a body vessel, such as a biliary or pancreatic duct, with reduced irritation to the body tissue, and which may be removed without damaging the body vessel. Furthermore, there exists a need for an improved method or procedure of implanting the drainage device without compromising the Sphincter of Oddi, and reducing the risk of duodenobiliary reflux.